Shoulda-Matchers + RSpec

mymodel_factory.rb

require ".../mymodel"

FactoryGirl.define do
  factory :mymodel, :class => MyModel do |m|
  end
end

mymodel_model.rb

class MyModel < ActiveRecord::Base
    validates :name, :presence => true, :format => { :with => /^(?:[a-zA-Z][a-zA-Z0-9]*)+(?:[\-_.][a-zA-Z][a-zA-Z0-9]*)*$/ }, :length => { :maximum => 255 }
  end
end

mymodel_spec.rb

describe MyModel do
  describe "something relevant" do
    subject { Factory.build(:mymodel) } # This model is an empty one. See the factory below
    it "does have a name" do
      should validate_presence_of(:name)
    end
  end
end